Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2011-07-25
Phys. Rev. B 84, 075450 (2011)
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
12 pages, 14 figures
Scientific paper
We re-examine the band structure of the stripe charge ordered state of $\alpha$-(BEDT-TTF)$_2$I$_3$ under pressure by using an extended Hubbard model within the Hartree mean-field theory. By increasing pressure, we find a topological transition from a conventional insulator with a single-minimum in the dispersion relation at the M-point in the Brillouin zone, towards a new phase which exhibits a double-minimum. This transition is characterized by the appearance of a pair of Dirac electrons with a finite mass. Using the Luttinger-Kohn representation at the M-point, it is shown that such a variation of the band structure can be described by an effective $2 \times 2$ low energy Hamiltonian with a single driving parameter. The topological nature of this transition is confirmed by the calculation of the Berry curvature which vanishes in the conventional phase and has a double peak structure with opposite signs in the new phase. We compare the structure of this transition with a simpler situation which occurs in two-component systems, like boron-nitride.
Kobayashi Akito
Montambaux Gilles
Piéchon Frédéric
Suzumura Yoshikazu
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